Various intravital saccharides play an important role in a mechanism for sustaining activities and lives of living organisms. In order to precisely reveal such functions of saccharides, the functions of saccharides need to be analyzed based on complex structures of the saccharides. The functions of saccharides are analyzed through a method in which an oligosaccharide whose structure has been revealed is used to reproduce a structure of the saccharide part by part so as to clarify a relationship between the structure and function of the entire saccharide.
The surface plasmon resonance (SPR) method is for example known as a method for analyzing functions of saccharides. That is, a ligand including an oligosaccharide which imitates a moiety of a saccharide is introduced onto a surface of a sensor chip. The sensor chip including the ligand introduced thereon is used to identify a substance such as a protein which specifically interacts with the oligosaccharide. This makes it possible to accurately evaluate a biological activity based on a structure of the oligosaccharide.
However, since a single molecule of oligosaccharide is not as active, oligosaccharides need to be collected on a sensor chip in case of evaluating a biological activity of the oligosaccharides. That is, collected oligosaccharides are used to analyze their interaction with a substance such as a protein, thereby making it possible to accurately evaluate a biological activity of the oligosaccharides.
Accordingly, as disclosed in Japanese Laid-Open Publication No. 836969/2003 (Tokukai 2003-836969; published on Mar. 19, 2003) (Document 1) and “Tentative Lecture Proceedings II in the 79th Spring Meeting, Chemical Society of Japan, Mar. 15, 2001, p. 1042” (Document 2), the inventors have so far obtained a linker compound whose molecule has a moiety immobilizable onto a sensor chip and a moiety capable of taking in an oligosaccharide. The inventors have also obtained a ligand which includes the linker compound and one unit (molecule) or two units of oligosaccharides introduced into the linker compound. Thus, the inventors have found that the ligand can collect oligosaccharides on a sensor chip and thereby introduce the oligosaccharides onto the sensor chip.
However, although the conventional ligand can arrange the sugar chain of the oligosaccharides two-dimensionally on a surface of the sensor chip, there is still a technical problem in that it is difficult to obtain the arrangement with high reproducibility.
That is, in case of collecting plural molecules of oligosaccharide on a surface of the sensor chip so as to analyze a biological activity of the oligosaccharides, the sugar chain of the oligosaccharides needs to be uniformly collected so as to observe with high reproducibility an interaction between the oligosaccharides and a protein. Particularly, in order to observe biological activities of the oligosaccharides, three to four units of oligosaccharides need to be collected on a surface of the sensor chip, and arranged two-dimensionally on the sensor chip with high reproducibility. This arrangement makes it possible to evaluate a biological activity of the oligosaccharides with high reproducibility.
However, the conventional ligand includes one or two units of oligosaccharides per one unit (molecule). In other words, in the conventional ligand, one linker compound binds to one or two oligosaccharides. Therefore, in order to observe a biological activity of the oligosaccharides, three or more units of oligosaccharides need to be collected on a surface of the sensor chip by collecting and arranging the ligands thereon in such a manner as to increase the ligand concentration.
In case of collecting oligosaccharides according to such a method, it is difficult to control the interval of the sugar chains of the oligosaccharides at a predetermined interval so as to obtain an oligosaccharide arrangement with high reproducibility. Therefore, with the conventional ligand, it is not possible to observe a biological activity of oligosaccharides with high reproducibility. This may cause a difficulty in revealing structures of saccharides, or evaluating biological activities of oligosaccharides.
The present invention was made to solve the above problems. It is an object of the present invention to provide a novel linker compound with which saccharides can be arranged two-dimensionally on a protein-analyzing supporter or the like with high reproducibility, a novel ligand which includes the linker compound and sugar molecules introduced thereinto, a ligand carrier, and a producing method thereof.